Comparative data on the histology of prostates from young, middle-aged, and old mice, of 24 inbred strains, and information from histological sections on pathological changes in the prostates of some old mice, will be analyzed. Included is an adenocarcinoma from a DBA/2J mouse, believed to be the first spontaneous prostatic tumor to be found in a mouse. The responses of cultures of prostatic epithelium, from dorsal and ventral lobes together or separately, to varoius hormonal supplements will be examined. Metabolic and nutritional studies on these cultures will also be made, in relation to the structure, function and ability to proliferate, of the cells. One objective will be to achieve a higher rate of cell proliferation, and thus enable us to establish cell lines, either of limited life span (presumably euploid and normal) or of unlimited potential, presumably in this case neoplastically transformed.